Gas turbine engines typically include inner flowpath surface elements that define a core flowpath for working gases. These surface elements are subject to high temperatures and are supported by a relatively cool engine structure. The different thermal environments require the inner flowpath surface elements to be thermally independent of the engine structure. Conventionally, the core flowpath defining surface elements are ring type hardware, such as nozzle vanes and turbine shrouds, that expand radially outward in response to temperature increases. Locator pins are conventionally used with the engine structure to retain these ring type flowpath surface elements in position circumferentially and axially relative to the engine structure while allowing for such radial thermal growth.
In addition to allowing for thermal growth of ring type engine members in the radial direction, a locator pin retention system should react axial and circumferential loads from the ring members in shear to minimize pin bending stress. Additionally, the pin should be removable so that the ring can be disassembled from the adjacent structure for repair and maintainability. The pin should also be locked in place during engine operation in order to prevent the pin from moving radially outward and thereby disconnecting from the ring.
FIG. 1 shows an existing pin retention system currently in use. This pin retention system utilizes a clip 10 that prevents radial outward movement of a pin 12. The pin 12 is seated in a tight tolerance interference fit hole 14 in an engine structure 16 to provide, with respect to the pin axis 13, shear loading in response to, with respect to engine centerline 17, circumferential and axial loading of a nozzle support segmented ring member 18. The clip 10 must be bent over manually in order to retain the pin 12. A disadvantage of this system is that the clip 10 must be made from a material that can be easily deformed for both installation and removal of the pin 12. The clip 10 therefore cannot resist a high degree of radial load that the pin 12 may exert, such as when the pin 12 binds in the inner ring member 18 and carries a load resulting from thermal growth of the inner member 18 radially outward.